Mentor Mothers (MMs) are women living with HIV who provide peer support to other HIV-positive women. MM programs have been incorporated into PMTCT programs in several African countries with some success, but with varying levels of MM training and program structure. The MoMent (MOther MENTor) study investigates whether highly-structured MM programs will further improve uptake and successful completion of PMTCT services (eg testing and appointments) in Nigeria. The study also evaluates the impact of structured MM programs on other outcomes, including facility deliveries, new infant HIV infections, infant survival and maternal viral suppression. Rural areas are the focus of this study because of their particularly poor performance in PMTCT coverage and outcomes.